Shroud assembly



Dec 25, 1962 H. w. WELSH 3,070,353

SHROUD ASSEMBLY Filed Dec. 3, 1958 2 Sheets-Sheet 1 [J INVENTOR! AT'TOHNE Y Dec. 25, 1962 H. w. WELSH 3,070,353

SHROUD ASSEMBLY Filed Dec. 3, 195a 2 Sheets-Sheet 2' IN VEN TOR.

Patented Dec. 25, 1962 3,070,353 SHROUD ASSEMBLY Harvey W. Welsh,Indianapolis, Ind., assignor to General Motors Corporation, Detroit,Mich., a corporation of Delaware Filed Dec. 3, 1958, Ser. No. 777,992 4Claims. (Cl. 25378) This invention relates to compressor and turbineconstructions.

More specifically, this invention relates to the construction of astator vane assembly for either a turbine or compressor of a gas turbineengine with particular attention being directed to the shroud ring forsupporting both the stator vanes and rotor blade abradable shroud rings.

This invention further relates to a shroud assembly constructed in amanner to be quickly and easily fitted within the compressor or turbinecasing. This invention accomplishes this objective by providing a shroudring with upstanding flanges having axial and radial crimped portionscircumferentially alternated thereon abutting depending axially spacedannular ridges secured to the compressor or turbine casing, thus bothaxially and radially locating the shroud ring with respect to thecasing.

Therefore, it is an object of this invention to provide a shroud ring ofthe type described with radial and axial crimped or crinkled portionscooperating with the turbomachine casing for axially and radiallylocating the shroud.

' Other features, advantages and objects will become apparent byreference to the detailed description of the invention and to thedrawings wherein there is shown the preferred embodiments of thisinvention.

In the drawings:

FIGURE 1 is a cross-sectional view of a portion of an engine casingtogether with the shroud rings embodying this invention,

FIGURE 2 is a perspective view of portions of two adjacent shroud rings,

FIGURE 3 is an enlarged view of a detail of FIGURE 1, and

FIGURE 4 is an enlarged cross-sectional view of a portion of the shroudring assembly of FIGURE 2.

Referring now more particularly to the figures, there is shown therein acasing of a gas turbine engine, which in this case may be either acompress or turbine casing enclosing the respective compressor orturbine. Formed as a part of the engine casing 10 are a number ofaxially spaced annular bosses or pads 12 having depending flanges orridges 14 extending internally of the casing.

Secured to the engine casing between adjacent flanges or ridges 14 bymeans to be described is a combined stator vane and rotor blade shroudring assembly 16 forming the subject of this invention.

Each assembly 16 comprises a plurality of circumferentially spacedstator vanes 18 secured by welding or other suitable means to an innershroud ring 20 and an outer shroud ring 22. The inner shroud ring 20 isformed as shown in an annular zigzag or labyrinth manner to provide forthermal expansion and sealing. The outer shroud 22 to which thisinvention is primarily directed includes an annular sheet metal plate 24stepped or rolled at one portion 26 to provide a recess 28 for theinsertion therein and securing thereto of an abradable ring 30constituting the rotor blade shroud ring. The plate 24 is beaded at 32for a purpose to be described and is bent at both edges to form radialoutwardly extending flanges 34 and 36.

Secured to both the flat portion and radial flange of plate 24 is asecond annular sheet metal plate 38 flanged and rolled at 40 and 42,respectively, and spot-welded to the plate 24 and flange 36 as shown toform a hollow box section 44 for supporting the stator vanes 18.Suitable apertures 46 equally spaced circumferentially around each ofthe plates 24 and 38 are provided therein for the insertion therethroughand welding thereto of the stator vanes 18, the apertures 46 in the twoplates being radially aligned and equal in number. Thus the stator vanesare securely held against axial and radial movement with respect to theshroud, and are located with respect to the rotor blades.

The radial flanges 34 and 36 are each crimped or ruflied at theiroutermost radial portions or edges as shown more clearly in FIGS. 2 and3 to provide an axial flange portion 48 alternating with a radial flangeportion 50, the two radial and axial portions being circumferentiallyalternated around the entire annulus. The axial and radial flanges 48and 50 are thus adapted to abut the radial and axial surfaces 52 and 54provided on the ridges 14 and pads 12, respectively, formed on thecasing 10. Thus, an axial and radial locating surface is provided foraxially and radially locating the stator vane and rotor blade shroudring with respect to the rotor blades 55 and casing 10. As shown, thealternate radially and axially crimped portions of each of the flanges34 and 36 face outwardly,

with the axial distance therebetween defining the axial width of theshroud section corresponding to the axial distance between the ridges14. As seen in FIGURE 3, the shroud plate 24, as mentioned previously,is rolled at 32 so as to underlie the ridge 14 and extend to a pointclosely adjacent the abradable rotor blade shroud 30 therefore acting asa gas seal to restrict communication of the hot motive fluid to theengine case 10. Thus, it will be seen that opposite edges of the shroudsections abut opposite face portions of the ridges 14.

While the shroud rings have been referred to as annular, by referring toFIGURE 4, it will be seen that these shroud rings are composed of twosegments having radially outwardly directed flanges 60 formed at eachend thereof for insertion into recesses 62 in the engine casing.Centrally of each shroud section, a threaded Pin 64 is welded thereto toplate 38 between the blade members andv extended through a suitableaperture 66 in the engine casing to be secured thereto by a nut 68. Theengine casing is also formed in two 180 segments with flanged portions70 at their abutting edges joined together by nut and bolt means 72, thenut and bolt means also securing the two flanged portions 60 of theshroud rings together.

To assemble the shroud ring of this invention, the an nular sheet metalring 24 is bent and rolled as shown to provide the two radial flanges 34and 36, the recess for the abradable rotor blade shroud and the axiallyextending portion 32. The outer portions of the flanges 34 and 36 arethen crimped as shown to provide circumferentially alternated axial andradial flanges 48 and 50. The sheet metal plate 38 is then formed asshown and secured to the plate 24. Slots are then cut in both the plates24 and 38, the abradable surface 30 is secured thereto, and the vanes 18are inserted through the slots and secured to the plates. The shroudring assembly now being complete, the radial and axial locating surfacesare then machined to fit the particular compressor case cooperating withthe ridges 14 and pads 12. The shroud ring assembly is then inserted inone half of the engine case with the flanges 48 and 50 abutting theradial and axial portions of ridges 14 and pads 12 thus radially andaxially locating the shroud ring with respect to the casing and rotorblades 55. The shroud ring is then secured to the engine casing by thenut 68 as seen in FIGURE 4. The other half of the engine case isassembled in the same manner, and the two segments are then positionedover the rotor of the turbine or compressor, whichever the case may be,and secured together by the nut and bolt means 72.

While the shroud ring has been defined as extending axially toprovide-for a rotor -blade shroud, -it willbe clear that this could beused just as a stator vane shroud without departing from the scope ofthe invention.

Thus, it will be seen that the crimped or deformed edges 48 and 50provide a machiningsurface that can bemachined accurately and easily toconform to the axial width between ridges 14 and the interior casediameter, therefore permitting easy and accurate assembly of the shroudring to the casing. Thus, the shroud can be machtned to fita particularinstallation and accommodates for any case distortion duringmanufacture.

From the foregoing it will be seen that thisinvention having internalmutually adjacent axially and radially facing locating surfaces; arelatively thin sheet metal shroud ring within said case having alocating surface contacting edge extending radially outwardly intocontact with said case locating surfacesgthe outer periphery of saidcontacting edge being annular and defined by circumferentiallyalternated radially and axially extending bent por' tons contactingrespectively the radially and axially facing locating surfaces on saidcase to radially and axially locate said shroud ring with respect tosaid case.

2. A turbomachine shroud ring locating assembly comprising, incombination, an annular turbomachine case.

having axially spaced ridges depending internally from said case, saidridges having opposite axial sides each side having mutually adjacentaxially and radially facing loeating surfaces, a plurality of relativelythin sheet metal shroud rings within said case each having a locatingsurface contacting flange extending radially outwardly from a oppositeaxial edges of said ring each into contact with a set of said caselocating surfaces, the outer periphery of each of said contactingflanges being annular and defined by circumferentially alternatedradially and axially extending bent portions contacting respectively theradially .1

and axially, facing locating surfaces on said case'with which theportions are associated to radially and axially locate said shroud ringwith respect to said case, the

shroud rings being axially adjacent each other to provide spaced sets ofmutually adjacent contacting flanges, the 1 different flanges of eachset of flanges being aligned with 5 and contacting different sides ofthe same case ridge.

3. A turbomachine shroud ring locating assembly com.- prising,incombination, an annular turbomachine case having axially spaced ridgesdepending internally from said case, said. ridges having opposite axialsides. each side having mutually adjacent axially and radially facinglocating surfaces, a plurality of relatively thin sheet metal shroudrings Within said case each having a locating surface contacting fiangeextending radially outwardly from opposite axial edges of said ring eachinto contact with a set of said case locating surfaces, the outerperiphery of each of said contacting flanges being annular and definedby circumferentially alternated radially and axially extending bentportions contacting respectively the radially and axially facinglocating surfaces on said case with which theportions are associated toradially and axially locate said shroud ring with respect to said case,the shroud ringsbeingaxially adjacent each other to provide spacedsetsof mutually adjacent contacting flanges, and means formed on one 0fthe flanges of one of said sets cooperating with the adjacent flange ofthe set to form a fluid sealtherebetween 'to restrict communication offluid radially outwardly from said rings to said case.

4. A turbomachine shroud ring locating assembly comprising,,incombination, an annular turbomachine case having internal mutuallyadjacent axially and radially ffiC',

ing locating surfaces, a relatively thin sheet metal shroud ring withinsaid case having a locating surface contacting edge extending radiallyoutwardly into contact with said case locating surfaces; the outerperiphery of said contacting edge beingannular and defined bycircumferentially alternated radially and axially, extending bentportions' contacting respectively theradially and axially fac- 1 inglocating surfaces on said case to radially and axially locate saidshroud ring with respect to said case, a plurality of circumferentiallyspaced stator vanes secured to said shroud fring, said shroud ringincluding axially extending means secured thereto and having a portionspaced therefrom together with said ring forming a tubular stator vanesupporting structure having radially inner and outer separated walls,said walls having apertures therein constituting guide means upon theinsertion of said stator vanes therein andtherethrough to axially locatesaid vanes with respect to said shroud ring.

References Cited in the file of this patent UNITED STATES PATENTS2,488,867: Judson Nov. 22, .1949" 2,507,079 Zimmerman May 9, 19502,658,719. Johanson Nov. 10, 1953 2,749,026 Hasbrouck et al June 5, 19562,766,963 Zimmerman. Oct. 16, 1956 2,771,622 Thorp Nov. 27, 19562,910,269 Haworthuetal. Oct. 27, 1959 FOREIGN PATENTS 975,879 FranceOct. 17, 1950 1,057,993- France- Nov, 4, 1953 789,733 Great, BritainJan. 29, 1958

